Fabrication and boiling heat transfer characterization of multi-scale microgroove surfaces

Microstructural functional surfaces play an important role in energy conversion applications including power generation, air conditioning, and thermal management of electronics through the boiling process. In this study, multi-scale microgroove surfaces were fabricated by the combination of wire electrical discharge machining (WEDM) and electrical discharge shaped machining (EDSM) to achieve a better boiling performance. The WEDM, with the advantage of high efficiency, was used to fabricate the first microgroove array, and rougher surfaces were formed by intense discharge. A wavy electrode was used in EDSM to fabricate the second microgroove array. Reentrant cavities at the intersections of microgrooves and rougher micro fins with spacing distribution were formed after EDSM. The boiling performance of the multi-scale microgroove surface was studied with water as the working medium under atmospheric pressure. The results indicated that the boiling performance of the microgroove surface is significantly enhanced. The critical heat flux and maximum heat transfer coefficient of microgroove surface were higher than the surfaces fabricated only by WEDM or EDSM, which were 2.34 and 3.29 times that of smooth copper plate, respectively. This study demonstrated that the combination of WEDM and EDSM is a convenient and effective method to fabricate high-performance microgroove boiling surfaces.